What is the key element in liqueur?

Answer 1

There isn't a 'key' element in liqueurs, but there is a key element to liqueurs. They all are a distillate of some kind of spirit with other by-products infused into the process (i.e. Irish cream liqueurs are Irish whiskies infused with cream and other flavorings). Most liqueurs are somewhat sweet, but not necessarily sugar infused. Also, the majority of liqueurs range from 10-25% alcohol by volume (20-50 proof). This is not to say that liqueurs can't be higher proof however, as some of the digestifs can range upwards of 100 proof. This can be somewhat confusing, given the fact that there are lots of products in other categories of the spirit world that are 'flavored', but are not considered a liqueur (i.e. flavored vodkas or rums, etc).